1. Field of the Invention
The present invention involves an adjustably insertable and retractable inlet guide vane apparatus for a compressor.
2. Description of the Prior Art
To improve the efficiency at predetermined power conditions of a compressor having a bladed rotor shaft, guide vanes are positioned in the inlet passage of the compressor. The vanes direct the incoming air flow to impinge upon the rotor blades at a predetermined swirl or angle of attack for optimum transfer of energy from the flow to the rotor shaft. These vanes ordinarily extend across the full width of the inlet passage and may be retractable at different load conditions to effect a changed swirl that is better suited for compressor operation at such conditions. The retraction of conventional retractable inlet guide vanes is generally accomplished by mechanical gearing actuated by a control unit.
The effectiveness of inlet guide vanes depends upon the angle of attack of the vane relative to the incoming flow and the load level of operation of the compressor. The overall efficiency of some compressor inlet configurations can be increased by the use of guide vanes extending only in that part of the inlet passage having the highest proportion of mass flow. However, when the vanes are inserted only part way across the inlet passage, recirculation of the incoming flow around the tip of the vane body can result in losses which reduce efficiency.